Generation of cortical neurons through reprogramming technology

The human cortex is affected by several debilitating acute and chronic neurodegenerative disorders such as stroke, traumatic brain injury, amyotrophic lateral sclerosis and Alzheimer’s disease, which target specific types of cortical neurons. Emerging evidence indicates that stem cells and reprogrammed cells can be used to generate human cortical neurons both for cell replacement by transplantation, and for disease modeling and drug screening. Several laboratories have established in vitro protocols for the derivation of excitatory pyramidal neurons, the principal type of neuron in the adult cortex, from human pluripotent stem cells (hPSCs). Efficient production of corticofugal projection neurons (CfuPNs) from ES cells has also been reported. Alternatively, human fibroblasts have been directly converted into induced neuronal (iN) cells. However, cortical neurons have not been produced by this method. Also, it remains to be assessed how closely the derived cortical neurons resemble their in vivo counterparts, as well as, whether the generated cells are capable of integrating into human neuronal circuits.The work presented in this thesis demonstrates that cortical neuronal cells can be produced from different types of starting cells: human fibroblasts, human ES cells and human iPSC-derived NSPCs. Regardless the starting cell context and derivation protocol, we have produced in all studies neuronal cells pyramidal in shape, expressing key cortical markers and functional in vitro. More importantly, we showed that these cells are capable of forming synaptic connections with adult human cortical neurons. It remains to be assessed whether cells derived in this thesis are capable of projecting to correct brain regions in vivo. Nonetheless, by providing the first evidence that cortical neurons derived here integrate in adult host neural networks also in a human-to-human grafting situation, this thesis represents an early but important step in the clinical translation of neuronal replacement to promote recovery in the injured brain